1. Field of the Invention
The present invention relates to a throttle body for executing an opening/closing operation of an air intake valve provided in an air intake passage of an internal combustion engine.
2. Description of the Related Art
There is generally well known a throttle body for controlling the opening degree of an air-intake throttling valve in accordance with the operation of an acceleration pedal (for example, see JP-A-10-196416).
In the throttle body shown in the above publication, a torque generated by a motor is transmitted to a valve shaft by a mechanical reduction gear to rotate a throttle valve fixed to the valve shaft, and an adjusting screw for adjusting a minute full-close air leakage amount under the full-close state of the air-intake passage and also executing a full-close opening degree adjustment of about 5° or less so as to prevent the throttle valve from biting the air-intake passage is fixed to a stopper portion for regulating the opening degree at the full-close side of the throttle valve. Furthermore, the stopper portion for regulating the opening degree under the full opening state constitutes a full-open stopper on the body wall surface while the position at which the opening degree of the throttle valve is set to be substantially parallel to the air-intake passage.
As disclosed in JP-A-10-196416, according to the conventional throttle body, an air-intake passage diameter is set in conformity with the maximum required air amount of the internal combustion engine while the air flow rate (amount) at the position at which the air resistance of the throttle valve is minimum (the state that the air-intake passage and the throttle valve are parallel to each other) is set as the maximum air flow rate. This is because the range of the opening degree from the full-close position of the throttle valve till the full-open position is larger, the control resolution when the throttle valve is driven by the motor is higher. Accordingly, in the conventional throttle body, the diameters of the air-intake passage and the throttle valve are determined according to the maximum required air flow rate of the internal combustion engine.
However, in the conventional setting method described above, it is required to prepare throttle bodies having air-intake passages and throttle valve diameters different every internal combustion engine in accordance with various maximum required air flow rates of internal combustion engines. Therefore, various kinds of bodies must be created, so that it is required to prepare various kinds of expensive metal molds. Furthermore, special designs are required for the air-intake valve, the shaft, etc., tooling change must be executed, and an exclusive line is required every machine type in some cases.
However, with respect to the internal combustion engines, there is a case where the control resolution is permitted to be lowered, and also there is a case where it is required to preferentially solve the problem that the cost is increased because the number of the types of throttle bodies is increased in conformity with the maximum required air amounts of the internal combustion engines.